In the art of catalytically hydrolyzing acrylonitrile with water to acrylamide, various copper and copper containing catalysts have been proposed, such as mixtures of copper oxide with other metal oxides, reduced copper oxide/metal oxide mixtures, copper and copper/metal mixtures (see U.S. Pat. Nos. 3,597,481; 3,631,104; 3,642,894; and 3,642,643). The use of Raney copper catalysts for this purpose is shown in Ger. Pat. No. 2,036,126, German DOS 2,164,185 (1972), Canadian Pat. 839,384 (1972) and apparently also in Asahi et al Japanese Publication 69/5205 (published April 3, 1969; filed May 13, 1966 as Jap. Application No. 66/29,948). Based upon the method of catalyst preparation, it would appear that such prior art can be cataloged into two groups, one group involving the reduction of a copper containing compound or compounds, the other group involving the activation of a copper or copper alloy (such as Raney copper). See also U.S. Pat. No. 3,767,706.
So far as can be determined, when using a Raney copper catalyst to hydrolyze acrylonitrile to acrylamide by the teachings of the prior art, it has been the practice to prepare such catalyst in the manner of Kawaken Fine Chemicals Co., Ltd. of Tokyo, Japan (see, for example, the above referenced Canadain Pat. No. 839,384 at p. 5 where it is indicated that the Raney copper catalyst there used was obtained from Kawaken Fine Chemicals Co.,). Kawaken Fine Chemicals Co. report in their trade literature that the starting alloy (for example a 50:50 weight ratio mixture copper and aluminum) is crushed, screened to size, and immersed into aqueous alkali to dissolve out virtually all of the aluminum, after which the resulting activated product is kept under water or inert solvents to avoid oxidation. Apparently complete aluminum removal was heretofore believed to be desirable for purposes of enhancing catalyst activity for this intended hydrolysis reaction.
A recent study of the immersion of such alloy particles into aqueous alkali suggests adverse effects upon catalyst activity are caused by overheating of alloy particles during activation with caustic. For example, when about 20 to 30 wt. % sodium hydroxide dissolved in water is contacted with starting alloy particles at the ratio of about 100 to 120 weight percent total caustic per 100 parts starting alloy particles with the alkali solution being maintained at a fixed temperature in the range from about 140 to 248.degree. F and with particle immersion time in such solution of 2 to 3 hours, heat is generated in a relatively short initial period in the immersion during which the aluminum is rapidly reacted away from the starting alloy. Presumably, the individual particles experience on their surfaces strong localized heating during this period. Such a thermal history, for reasons not altogether clear, is apparently responsible for a reduction in the catalytic activity of the product caustic-activated Raney copper catalyst in the catalytic hydrolysis in water of acrylonitrile to acrylamide. Such product catalyst produced by such immersion contains not more than about 0.5 weight percent aluminum on a 100 weight percent basis and this catalyst is typically in the form of a finely divided solid material.
Apparently, prior art Raney copper catalysts are prepared by changing starting alloy particles to a caustic solution. These particles are usually small in size to enhance and accelerate aluminum dissolution from the starting alloy and achieve thereby a maximum removal of aluminum initially present in such starting particles. This small particle, caustic activated product catalyst may be better suited for use as a suspension catalyst (see Mitsui Toatsu Chemicals, Ger. DOS 2,240,783) than as a fixed bed catalyst in such hydrolysis reaction. The characteristically low activity of catalysts produced in this manner just described dictates the use of a high surface area catalyst system, i.e. a system of very small catalyst particles, to enhance the hydrolysis rate of acrylonitrile to acrylamide (independently of reactant relative concentrations). These prior art catalyst particles have typically a limited or relatively low initial catalyst activity, and also have a relatively short half life. They are shown in the prior art on acrylonitrile hydrolysis to acrylamide to operate on dilute, starting aqueous acrylonitrile feeds.
Recent studies of Raney copper catalysts used in the art of hydrolyzing acrylonitrile to acrylamide show that the conditions of activation exert a profound influence upon the properties of the product catalyst in nitrile hydrolysis. Because of the limitations and shortcoming above indicated for prior art Raney copper catalysts, the art continues to seek a Raney copper catalyst adapted for such hydrolysis reaction which has a high initial activity and a long activity half life, and which, additionally, is particularly well suited for hydrolyzing acrylonitrile in a concentrated acrylonitrile/water feed at a rapid rate and at a high conversion level. Preferably, it would be beneficial to the art to have a Raney copper catalyst with such properties which, in addition, could readily be and conveniently prepared in particle sizes large enough to permit use of the activated product a fixed catalyst bed, as opposed to a suspension or fluidized bed system, for example.